Description
Adenosine(58-61-7) is a nucleoside composed of a molecule of adenine attached to a ribose sugar molecule (ribofuranose) moiety via a β-N9-glycosidic bond. Adenosine works in the energy transfer-as adenosine triphosphate (ATP) and adenosine diphosphate (ADP)-as well as in signal transduction as cyclic adenosine monophosphate, cAMP. It shows neuromodulatory, cytoprotective, anti-inflammatory and cardioprotective actions.
Chemical Properties
Adenosine is an important nucleoside composed of adenine and ribose. White, crystalline, odorless powder, mild, saline, or bitter taste, quite soluble in hot water, practically insoluble in alcohol. Formed by isolation following hydrolysis of yeast nucleic acid.
Definition
ChEBI: Adenosine is a ribonucleoside composed of a molecule of adenine attached to a ribofuranose moiety via a beta-N(9)-glycosidic bond. It has a role as an anti-arrhythmia drug, a vasodilator agent, an analgesic, a human metabolite and a fundamental metabolite. It is a purines D-ribonucleoside and a member of adenosines. It is functionally related to an adenine.
Brand name
Adenocard (Astellas); Adenoscan (Astellas).
Origin
Adenosine may be generated intracellularly in the central nervous system from degradation of AMP or from the hydrolysis of S-adenosyl homocysteine, and then exit via bi-directional nucleoside transporters, or extracellularly by the metabolism of released nucleotides. Inactivation of extracellular adenosine occurs by transport into neurons or neighboring cells, followed by either phosphorylation to AMP by adenosine kinase or deamination to inosine by adenosine deaminase[1].
Biological Functions
Adenosine regulates multiple physiological and pathophysiological processes, by acting both through G-protein coupled adenosine receptors and intracellularly. It modulates neuronal plasticity, astrocytic activity , learning and memory, food intake, motor function, sleep/wake cycle, pain, immunosupression, proliferation, and aging. Adenosine is involved in ischemia and stroke, epilepsy, and neurodegenerative pathologies such as Parkinson's disease (PD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). Extracellular adenosine, interacting with P1 receptors (A1R, A2AR, A2BR, and A3R) regulates metabolism through different signaling pathways[1].
Biological Functions
[1] Mercedes Garcia-Gil. “Metabolic Aspects of Adenosine Functions in the Brain.” Frontiers in Pharmacology (2021): 672182.
General Description
Adenosine is a purine nucleoside and a building block of RNA and many other biomolecules such as adenosine triphosphate and nicotinamide adenine dinucleotide. In the extracellular space, ecto-5′-nucleotidase (CD73) dephosphorylates adenosine triphosphate (ATP) to produce adenosine. Adenosine has four receptors namely A1R, A2AR A2BR and A3R. Adenosine plays a key role in the osteogenic differentiation. A1R induces osteoclast differentiation and A2AR induces osteoblast differentiation.
Biological Activity
Neurotransmitter that acts as the preferred endogenous agonist at all adenosine receptor subtypes.
Biochem/physiol Actions
Endogenous neurotransmitter at adenosine receptors. Cardioprotective effects may relate to activation of A1 adenosine receptors. The antiplatelet and anti?inflammatory actions of adenosine appear to be mediated via the A2 adenosine receptor. In contrast, adenosine appears to be a pro-inflammatory mediator in asthma and chronic obstructive pulmonary disease (COPD).
Clinical Use
Adenosine (Adenocard) is an endogenous nucleoside
that is a product of the metabolism of adenosine triphosphate.
It is used for the rapid termination of supraventricular
arrhythmias following rapid bolus dosing.
Adenosine is approved for the acute management and
termination of supraventricular tachyarrhythmias, including A-V nodal reentrant tachycardia and A-V reciprocating
tachycardia. Adenosine may be helpful in the
diagnosis of atrial flutter.
Side effects
Adverse reactions to the administration of adenosine are
fairly common; however, the short half-life of the drug
limits the duration of such events.The most common adverse
effects are flushing, chest pain, and dyspnea.
Adenosine may induce profound bronchospasm in patients
with known reactive airway disease. The mechanism
for bronchospasm is unclear, and the effect may last
for up to 30 minutes despite the short half-life of the drug.
Drug interactions
Metabolism of adenosine is slowed by dipyridamole, indicating
that in patients stabilized on dipyridamole the
therapeutically effective dose of adenosine may have to
be increased. Methylxanthines antagonize the effects of
adenosine via blockade of the adenosine receptors.
Metabolism
It is impossible to study adenosine in classical
pharmacokinetic studies, since it is present in various
forms in all the cells of the body. An efficient salvage
and recycling system exists in the body, primarily in
erythrocytes and blood vessel endothelial cells. The halflife in vitro is estimated to be less than 10 seconds, and
may be even shorter in vivo.
Purification Methods
Crystallise adenosine from distilled water and dry it at 110o. It has been purified via the picrate, where ethanolic picric acid is added to adenosine and the picrate is filtered off and recrystallised from EtOH. It has m 180-185o(dec). Adenosine is recovered by dissolving 0.4g of the picrate in 80mL of hot H2O, treated with a small quantity of Dowex 1 anion exchange resin in the chloride form, and the resin is filtered off. The filtrate is treated with more resin and filtered again. One equivalent of aqueous NaOH is added to the colourless filtrate which is evaporated to 4mL and cooled to give 0.176g of adenosine m 236o. [Davoll et al. J Chem Soc 967 1948, Davoll & Lowy J Am Chem Soc 73 1650 1951, Beilstein 26 III/IV 3598.]
Precautions
Patients with second- or third-degree A-V block should
not receive adenosine. As indicated previously, the use
of adenosine in asthmatic patients may exacerbate the
asthmatic symptoms.
